PERTH, Australia (AP) _ Russia's Alex Popov turned up the heat on Australian training partner Michael Klim, winning the 100-meter freestyle today in the world swimming championships.

Popov, a four-time Olympic gold medalist, made the turn first and was never seriously threatened by Klim. Both are coached by Russia's Gennadi Touretski and train together at the Australian Institute of Sport.

Popov, 26, is attempting to become the first man to win both the 50 and 100 in successive world meets. He achieved the Olympic double for the second consecutive time at Atlanta. The 50 is Saturday.

``I'm exhausted, but not ecstatic,'' Popov said. ``It was a usual victory, nothing spectacular.''

Popov finished in 48.93 seconds, while Klim, who won the 200 freestyle and was a member of the winning 800 freestyle relay team, was second in 49.20. Lars Frolander of Sweden followed in 49.53.

The Russian said after the race that he felt he was tiring near the end.

``I said to Michael, `I think I lost half a second in the last 10 meters,''' Popov said. ``I couldn't feel anything in my body anymore.''

Klim said he didn't pay much attention to his rival during the race.

``I was really only concentrating on myself, and not on Alex,'' Klim said. ``I didn't see him. It's his event and he really deserves it. I might have to wait for the next generation.''

Popov, who set the world record of 48.21 in June 1994 at Monte Carlo, appears to be back at his best after being seriously injured in a Moscow knife attack shortly after the Atlanta Games.

China's Chen Yan took the women's 400 freestyle for her second gold medal of the meet, and Lia Maurer of Crestwood, N.Y., won the 100 backstroke.

Chen finished in 4:06.72. Brooke Bennett of Plant City, Fla., who led through 300 meters, was second in 4:07.07, and Dagmar Hase of Germany finished third in 4:08.82.

Chen gave China, troubled by a drug scandal, its only other pool gold so far when she took the 400 individual medley Monday.

Bennett, 17, the 800 winner in Atlanta, set the pace through every change until Chen took over just before the final 50 meters.

``I tried to stay with the Chinese girl all the way,'' Bennett said. ``But I saw her just getting away from me at the end.''

Chen's victory will help dispel rumors that poor performances by her teammates might be the result of a drug seizure in Sydney.

Last Thursday, swimmer Yuan Yuan was caught holding enough drugs to keep her country's pool team supplied for the week-long world championships.

Yuan and coach Zhou Zewen, who both appeared before a doping panel Saturday, were called home from the world championships Friday after tests confirmed Yuan was trying to import a banned growth hormone.

Maurer won the 100 backstroke in 1:01.16. Japan's Mai Nakamura finished second in 1:01.28, and Germany's Sandra Voelker was third in 1:01.47. Beth Botsford of Baltimore was fifth in 1:02.31.

Ukraine's Denys Sylantyev won the men's 200 butterfly in 1:56.61. France's Franck Esposito was second in 1:56.77, and Tom Malchow of St. Paul, Minn., finished third in 1:57.26.

In synchronized swimming, Olga Brousnikina and Olga Sedakova won the duet title. Sedakova won the solo event Tuesday.